Resumen
In a few words, item response theory (IRT) postulates that (a) examinee test performance can be predicted (or explained) by a set of factors called traits, latent traits, or abilities, and (b) the relationship between examinee item performance and these traits can be described by a monotonically increasing function called and item characteristic function. This function specifies that examinees with higher scores on the traits have higher expected probabilities for answering an item correctly than examinees with lower scores on the traits. In applying item response theory to measurement problems, a common assumption is made that there is one dominant factor or ability which can account for item performance. This so-called "ability" which the test measures could be a broadly or narrowly defined aptitude, achievement, or personality variable.
